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    Re: More on Thomas Hubbard Sumner
    From: Fred Hebard
    Date: 2005 Feb 10, 16:12 -0500

    On Feb 10, 2005, at 4:04 PM, George Huxtable wrote:
    > A posting from Trevor ended-
    >> None of which goes anywhere towards explaining why an educated
    >> mathematician and astronomer, with the smarts to understand what was
    >> under his nose, was navigating a ship off the Smalls on the morning of
    >> 17 December 1837. And that is the real question at hand.
    > ========================
    > I wonder if a point is being missed in all this discussion about
    > Sumner.
    > What surprises me, is that it took until 1837 for navigators to realise
    > that a useful position line could be drawn from a single observation
    > of the
    > altitude of a body, even if it wasn't at meridian passage.
    > But it still surprises me: why, oh why, did it take so long for
    > intelligent
    > men to discover such a simple matter?
    > George.
    Could the absence of a chronometer have been the limiting factor? Those
    great minds were testing celestial methods, not chronometers.  Lunars
    can get you time to the nearest 30 seconds or so.  Don't you need time
    to the nearest 1-5 seconds to get accurate fixes away from meridian
    passage?  Thirty seconds puts you out up to 7-8 miles, if I recall
    correctly.  Was that too inaccurate to consider position line methods?
    Also, how long did it take seamen to start trusting the chronometer?
    This is not to mention that fixes were for latitude only and longitude
    only.  How many were thinking of position lines other than lat-long
    lines?  How many were thinking of the geographical position of a
    celestial body?

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